DC Servo Motor Speed Control

The speed of the servo motor can be controlled by variying the input supplys frequency.

normaly the input to servo is of square pulse so i have got some useful links for you

try this..

http://www.seattlerobotics.org/guide/servos.html

http://www.seattlerobotics.org/encoder/200009/S3003C.html

http://www.mcmanis.com/chuck/Robotics/projects/servo.html

http://www.aptronix.com/fuzzynet/applnote/servo.htm

http://www.worldservo.com/html/arc.htm

....

How many amps does your motor draw? I imagine you want something very simple, right? Or is this a fun project that you want to learn from?

Thanks Everybody for your comments about the servo speed control. The motor draws 6 amps and is rated at 24V DC. I have it sussed now. I am building a PWM controller based on a 555 timer. I think that this will work for me as I only need to slow the motor down. I do not need any feedback for this project. As a mater of interest for some of you, the motor I am using is off a CNC machine and it has a rotary encoder on the back of it. It also has a 24:1 ratio gearbox built on to it.

Sorry about the delay in getting back to you as I was away for a few days.

once again thanks to all who replied, it is greatly appreciated.

The speed can be controlled accurately by counting the steps on the encoder.

For your application slight variations would not matter.

A stepper motor can also be used (a scraped pen plotter can be adapted for the controller).

CAUTION! Make sure the pig is dead otherwise it might take your roasted potatoes or other food every time it comes around.

DemCon,

Depending on the particular servo motor, since the load will be relatively small, you may be able to get by fine just by reducing the voltage. If it doesn't exhibit any signs of overheating, your done.

Alternately, you could construct a large rotating frame in which you could, with carefully directed blowers and reflectors, keep your pig stationary in the center, while you rotate the fire around it.

Regards, Greg

I've used a car windscreen wiper motor for similar purposes, it has a worm drive gear built in and can operate at very high power levels.

Also they usually have two windings for fast and slow operation. speed control is easily done by varying the dc voltage drive...

John.

Try running it off a 12V car battery or charger. If the speed is O. K. then problem is solved. If too fast, try 6 VDC charger.

I have built a few simple PWM controllers for motors before. Just watch the supply voltage as a lot of the 555's are limited to 16 VDC or so, whereas your FET will likely handle a lot more.

I used IRFZ44V MOSFETs, Great for this kind of thing.